Surfactant peptide nanostructures, and uses thereof

ABSTRACT

This work describes a new class of short polypeptides that can self-assemble to form regular nanotubes with an average diameters of about 50 nm. These peptides (7 to 8 amino acids) have a structure very similar to those observed in surfactant molecules with a defined hydrophilic head group constituting of charged amino acids and a lipophilic tail made out of hydrophobic amino acids such as alanine, valine or leucine. Cryo-TEM micrographs show numerous three-fold junctions connecting the self-assembling nanostructures and thus leading to the formation of a rather dense network of entangled nanotubes. Additionally, the observation of clear openings at the end of the supramolecular structures confirms the presence of tubular organization.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/192,832, filed Jul. 10, 2002, which claims the benefit of U.S.Provisional Application No. 60/304,256, filed on Jul. 10, 2001. Theentire teachings of the above application(s) are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to dipolar oligopeptides that self assemble toform very regular structures. The invention also relates to methods offorming gold nanostructures by localizing gold upon the self assembledstructures of the present invention. The invention also relates tomethods of delivering drugs and other guest compounds across a hostmembrane using the self assembled structures of the present invention.The invention also relates to filtration systems based on nanotubes ofthe present invention. The invention also relates to pharmaceuticalcompositions comprising a compound of the present invention.

BACKGROUND OF THE INVENTION

Molecular self-assembly is the spontaneous organization of moleculesinto structurally well-defined arrangements due to non-covalentinteractions. The resulting supramolecular structure usually providesnanoarchitectures with very defined macroscopic properties¹. As aresult, molecular assemblies have attracted much attention in relationto the development of novel materials. In the last decade, molecularself-assembly of biopolymer has shown to play a key role in thediscovery and design of biomaterials finding applications in the fieldof medical technology such as, e.g., regenerative medicine and drugdelivery systems^(2,3). Recently, among the different systemsinvestigated, a new class of ionic self-complementary oligopeptide hasattracted a great deal of attention due to their ability tospontaneously self-assemble to form stable macroscopic structure in thepresence of monovalent cations⁴.

A number of peptide molecular self-assembly systems have been designedand developed (Table 1). This systematic analysis provided insight intothe chemical and structural principles of peptide self-assembly. Thesepeptides are short, simple to design, extremely versatile and easy tosynthesize. Three types of self-assembling peptides have beensystematically studied thus far. It is believed additional differenttypes will be discovered and developed in the coming years. This classof biological materials has considerable potential for a number ofapplications, including scaffolding for tissue repair and regenerativemedicine, drug delivery of molecular medicine, as well as biologicalsurface engineering. Similar systems have also been described wherethese peptide systems undergo self-assembly to form gel with regularβ-sheet tapes of well-defined structures⁵. The self-assembly of peptidenanotubes that allow ions to pass through and to insert themselves intolipid bilayer membrane were also described^(6,7). Furthermore a numberof fascinating biomimetic peptide and protein structures have beenengineered, such as helical coil-coils, di-, tri- and tetra-helicalbundles^(8,10). However, their applications for materials science andengineering remain under explored. It is likely that these stable coiledcoils will be developed as nanomaterials in the future.

Type I Self-assembling Peptides

Type I peptides, also called “molecular Lego”, form β-sheet structuresin aqueous solution because they contain two distinct surfaces, onehydrophilic, the other hydrophobic. See U.S. Pat. No. 5,670,483. LikeLego bricks that have pegs and holes and can only be assembled intoparticular structures, these peptides can do so at the molecular level.The unique structural feature of these peptides is that they formcomplementary ionic bonds with regular repeats on the hydrophilicsurface. The complementary ionic sides have been classified into severalmoduli, i.e. modulus I, II, III, IV, etc., and mixed moduli. Thisclassification is based on the hydrophilic surface of the molecules thathave alternating + and − charged amino acid residues, either alternatingby 1, 2, 3, 4 and so on. For example, molecules of modulus I have − +− + − + − +, modulus II, − − + + − − + +, modulus, IV − − − − + + + +.These well defined sequences allow them to undergo orderedself-assembly, resembling some situations found in well studied polymerassemblies.

Upon the addition of monovalent alkaline cations or the introduction ofthe peptide solutions into physiological media, these oligopeptidesspontaneously assemble to form macroscopic structures that can befabricated into various geometric shapes¹¹. Scanning EM reveals that thematrices are made of interwoven filaments that are about 10-20 nm indiameter and pores about 50-100 nm in diameter^(12,13).

The molecular structure and proposed complementary ionic pairings of theType I peptides between positively charged lysines and negativelycharged glutamates in an overlap arrangement represent an example ofthis class of self-assembling β-sheet peptides that spontaneouslyundergo association under physiological conditions. If the chargedresidues are substituted, i. e., the positive charged lysines arereplaced by positively charged arginines and the negatively chargedglutamates are replaced by negatively charged aspartates, there areessentially no drastic effects on the self-assembly process. However, ifthe positively charged resides, Lys and Arg are replaced by negativelycharged residues, Asp and Glu, the peptide can no longer undergoself-assembly to form macroscopic materials although they can still formβ-sheet structures in the presence of salt. If the alanines are changedto more hydrophobic residues, such as Leu, Ile, Phe or Tyr, themolecules have a greater tendency to self-assemble and form peptidematrices with enhanced material strength¹³.

A number of mammalian cells have been tested and all have been found tobe able to form stable attachments with the peptide materials¹¹. Severalpeptide materials have been used to test for their ability-to supportcell proliferation and differentiation. These results suggested that thepeptide materials can not only support various types of cellattachments, but can also allow the attached cells to proliferate anddifferentiate. For example, rat PC12 cells on peptide matrices wereexposed to NGF, they underwent differentiation and exhibited extensiveneurite outgrowth. In addition, when primary mouse neuron cells wereallowed to attach the peptide materials, the neuron cells projectedlengthy axons that followed the specific contours of the self-assembledpeptide surface.

The fundamental design principles of such self-assembling peptidesystems can be readily extended to polymers and polymer composites,where co-polymers can be designed and produced.

Type II Self-assembling Peptides

Several Type II peptides are developed as “Molecular Switches” in whichthe peptides can drastically change its molecular structure. One of thepeptides with 16 amino acids, DAR16-IV, has a β-sheet structure atambient temperature with 5nm in length but can undergo an abruptstructural transition at high temperatures to form a stable a-helicalstructure with 2.5 nm length¹⁴. Similar structural transformations canbe induced by changes of pH. This suggests that secondary structures ofsome sequences, especially segments flanked by clusters of negativecharges on the N-terminus and positive charges on the C-terminus, mayundergo drastic conformational transformations under the appropriateconditions. These findings can not only provide insights intoprotein-protein interactions during protein folding and the pathogenesisof some protein conformational diseases, including scrapie,Huntington's, Parkinson's and Alzheimer's disease, but also can bedeveloped as molecular switches for a new generation of nanoactuators.

The peptides of DAR16-IV (DADADADARARARARA) and EAK12 (AEAEAEAEAKAK)have a cluster of negatively charged glutamate residues close toN-terminus and a cluster of positively charged Arg residues nearC-terminus. It is well known that all α-helices have a helical dipolemoment with a partial negative C-terminus toward a partial positiveN-terminus¹⁵. Because of the unique sequence of DAR16-IV and EAK12,their side chain charges balance the helical dipole moment, thereforefavoring helical structure formation. However, they also havealternating hydrophilic and hydrophobic residue as well ionicself-complementarity, which have been previously characterized to formstable β-sheets. Thus the behavior of this Type II of molecules islikely to be more complex and dynamic than other stable β-sheetpeptides. Additional molecules with such dipoles have been designed,studied and confirmed the initial findings.

Others have also reported similar findings that proteins and peptidescan undergo self-assembly and disassembly or change their conformationsdepending on the enviromnental influence, such as its location, pHchange and temperature or crystal lattice packing^(16,18).

Type III Self-assembling Peptides

Type III peptides, like “Molecular Paint” and “Molecular Velcro”;undergo self-assembly onto surface rather with among themselves. Theyform monolayers on surfaces for specific cell pattern formation or tointeract with other molecules. These oligopeptides have three distinctfeatures. The first feature is the terminal segment of ligands thatincorporate a variety of functional groups for recognition by othermolecules or cells. The second feature is the central linker where avariable spacer is not only used to allow freedom of interaction at aspecified distance away from the surface but also permit the flexibilityor rigidity. The third feature is the surface anchor where a chemicalgroup on the peptide can react with the surface to form a covalent bond.This simple system using Type III self-assembly peptides and othersubstances to engineer surfaces is an emerging technology that will be auseful tool in biomedical engineering and biology. This biologicalsurface engineering technique will provide new methods to studycell-cell communication and cell behavior¹⁹.

Other previously pioneered molecular self-assembly systems through theincorporation of organic linkers for surface anchoring have beendeveloped by George Whitesides and his colleagues¹. TABLE 1 Type Iself-assembling peptides studied. Ionic Struc- Name Sequence (N→C)Modulus ture RADA16-I   + − + − + − + − I β n-RADARADARADARADA-cRGDA16-I   + − + − + − + − I r.c. n-RADARGDARADARGDA-c RADA8-I   + − + −I r.c. n-RADARADA-c RAD16-II   + + − − + + − − II β n-RARADADARARADADA-cRAD8-II   + + − − n-RARADADA-c II r.c. EAKA16-I    − + − + − + − +n-AEAKAEAKAEAKAEAK-c I β EAKA8-I    − + − + n-AEAKAEAK-c I r.c. RAEA16-I  + − + − + − + − n-RAEARAEARAEARAEA-c I β RAEA8-I   + − + −n-RAEARAEA-c I r.c. KADA16-I   + − + − + − + − n-KADAKADAKADAKADA-c I βKADA8-I   + − + − n-KADAKADA-c I r.c. EAH16-II    − − + + − − + +n-AEAEAHAHAEAEAHAH-c II β EAH8-II    − − + + n-AEAEAHAH-c II r.c.EFK16-II    − − + + − − + + n-FEFEFKFKFEFEFKFK-c II β EFK12-I    − + − +− + n-FEFKFEFKFEFK-c I β EFK8-II    − + − + n-FEFKFEFK-c I β ELK16-II   − − + + − − + + n-LELELKLKLELELKLK-c II β ELK8-II    − − + +n-LELELKLK-c II β    − − + + − − + + EAK16-II n-AEAEAKAKAEAEAKAK-c II β   − − − − + + EAK12 n-AEAEAEAEAKAK-c IV/II α/β EAK8-II    − − + +n-AEAEAKAK-c II r.c. KAE16-IV   + + + + − − − − n-KAKAKAKAEAEAEAEA-c IVβ EAK16-IV   − − − − + + + + n-AEAEAEAEAKAKAKAK-c IV β KLD12-I   + − +− + − n-KLDLKLDLKLDL-c I β KLE12-I   + − + − + − n-KLELKLELKLEL-c I βRAD16-IV   + + + + − − − − n-RARARARADADADADA-c IV β DAR16-IV   − − −− + + + + n-ADADADADARARARAR-c IV α/β DAR16-IV*    − − − − + + + +n-DADADADARARARARA-c IV α/β DAR32-IV     − − − − + + + +n-(ADADADADARARARAR)-c IV α/β EHK16   +−+−+++++−+−++++n-HEHEHKHKHEHEHKHK-c N/A r.c. EHK8-I   +−+−++++ n-HEHEHKHK-c N/A r.c.VE20*    − − − − − − − − − − n-VEVEVEVEVEVEVEVEVEVE-c N/A β (NaCl) RF20*   + + + + + + + + + + n-RFRFRFRFRFRFRFRFRFRF-c N/A β (NaCl)β, β-sheet; α, α-helix; r.c., random coil; N/A, not applicable. Thenumbers follow the name denote thelength of the peptides.*Both VE20 and RF20 are in β-sheet form when they are incubated insolution containing NaCl. They do not self-assemble to form macroscopicmatrices.β,β-sheet; α, α-helix; r.c., random coil; N/A, not applicable. Thenumbers follow the name denote the length of the peptides. *Both VE20and RF20 are in β-sheet form when they are incubated in solutioncontaining NaCl. They do not self-assemble to form macroscopic matrices.

In another attempt to exploit the intrinsic self-assembly ofpolypeptides as a new avenue to supramolecular materials, Aggeli et al.have designed different short oligopeptides that self-assemble, innon-aqueous solvent, into long, semi-flexible, polymeric β-sheetnanoptapes⁵. These systems were rationally designed to provide strongcross-strands attractive forces between the side chains such aselectrostatic interactions, hydrophobic interactions orhydrogen-bondings. In another study, Ghadiri and co-workers haveproduced self-assembling nanotubes made from cyclic D,L-α-peptides andcyclic β-peptide. They first showed the evidence that D,L-cyclic peptidesubunits (cyclo[-(L-Gln-D-Ala-L-Glu-D-Ala)₂-]) adopt flat, ring-shapedconformations and stack through backbone-backbone hydrogen bonding toform extended cylindrical structures²⁰.

SUMMARY OF THE INVENTION

The present invention describes a new type of short oligopeptidcs anddi- and tri-block peptide copolymers whose properties closely mimicthose found in surfactant molecules. The objective being to form newself-assembled nanostructures, very similar to those observed insurfactant solutions. It is well known that most surfactants areamphiphilic molecules that tend to aggregate in order to isolate thehydrocarbon chain from the contact with water. The common feature forthis self-association is the formation of a polar interface, whichseparates the hydrocarbon and water regions. Perhaps the most commonstructure formed in water is the spherical micelle consisting oftypically 50-100 lipid molecules arranged so that their hydrocarbontails form the interior of the micelle, and the polar head groups act asa shield against the surrounding water. The micelle, however, is onlyone of many aggregate types formned. Depending on the surfactant and itsconcentration, various structures are found, including liposomes,lamellar phase, hexagonal and cubic structures. Among the latter,liposomes have attracted a particular interest due to its potentialutility for conventional drug delivery.

The initial results based on the self-assembly of short amphiphilicpeptides have shown very defined structures of about 50 nm. It has alsobeen observed that these self-assembled structures can be modified byexternal parameters such as pH. Moreover, an adequate design of thepeptide allows fine-tuning the self-assemblies properties, giving a highflexibility for various potential applications. Regarding thesedifferent issues, the development of controllable and reproducibleliposomal systems for systematic drug delivery system has beenrelatively ineffective. In this context, it is strongly believed thatstructures based on oligopeptides self-assemblies may have the abilityto entrap and deliver molecules with a high degree of efficiency andthus could open innovative avenues for novel drug/gene delivery systems.

In certain embodiments, the compounds of the present invention arerepresented by the following formnulas: Sequence (N → C) Formula(φ)_(m)(+)_(n) 1 (+)_(n)(φ)_(m) 2 (φ)_(m)(−)_(n) 3 (−)_(n)(φ)_(m) 4(−)_(n)(φ)_(m)(−)_(n) 5 (+)_(n)(φ)_(m)(+)_(n) 6 (φ)_(m)(−)_(n)(100 )_(m)7 (φ)_(m)(+)_(n)(φ)_(m) 8 (+)_(n)(φ)_(m)(−)_(n) 9 (−)_(n)(φ)_(m)(+)_(n)10wherein

(φ) represents amino acids, natural or non-natural, containing nonpolar,noncharged sidechains;

(+) represents amino acids, natural or non-natural, containing cationicsidechains at physiological pH;

(−) represents amino acids, natural or non-natural, containing anionicsidechains at physiological pH;

m represents an integer >5; and n represents an integer >1.

In certain embodiments, the present invention provides self-assembledstructures comprising compounds of formulas 1-10.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts molecular models of surfactant peptide monomers. A) A₆D;B) V₆D; C) A₆D₂; D) V₆D₂; and E) L₆D₂ (See Table 1).

FIG. 2 depicts low resolutions of Cryo-TEM image of surfactant peptidesat pH 7. The peptide concentrations are 5 mg/ml.

FIG. 3 depicts low resolution of Cryo-TEM image of the aqueous solutionof V₆D.

FIG. 4 depicts Cryo-TEM images of the A₆D at high resolution.

FIG. 5 depicts a structural organization suggested by molecular modelingof the peptide nanotube.

DETAILED DESCRIPTION OF THE INVENTION

The present invention aims to describe the extraordinary self-assemblybehavior of a new type of surfactant-like peptides. This class ofpeptides has been designed and investigated for their ability tospontaneously self-assemble to form stable nanotubes. These shortpeptides (7 to 8 amino acids) have a structure very similar to thoseobserved in surfactant molecules with a defined hydrophilic head groupconstituted of charged amino acids and a lipophilic tail made out ofhydrophobic amino acids such as alanine, valine, isoleucine or leucine.As a result, when dispersed in water, the amphiphilic peptides tend toself-assemble in order to isolate the hydrophobic tail from the contactwith water. The common feature for this self-assembly is the formationof a polar interface, which separates the hydrocarbon and water regions.

Definitions

For convenience, certain terms employed in the specification, examples,and appended claims are collected here.

The amino acids will be represented by their commonly assigned letterdesignations:

A for alanine, C for cysteine, D for aspartic acid, E for glutamic acid,F for phenylalanine, G for glycine, H for histidine, I for isoleucine, Kfor lysine, L for leucine, M for methionine, N for asparagine, P forproline, Q for glutamine, R for arginine, S for serine, T for threonine,V for valine, W for tryptophan, and Y for tyrosine.

The term “amphiphilic” refers to a molecule which has a polar headattached to a long hydrophobic tail, or a molecule that has a polarsegment and a nonpolar segment.

The term “axial ratio” refers to the ratio of the length of the selfassembled structure to one of the lateral axes taken as unity.

The term “cryo-transmission electron microscopy” refers to a form ofmicroscopy done at low temperatures, usually at −160° C. to −50° C.,where the specimen transmits an electron beam focused on it, imagecontrasts are formed by the scattering of electrons out of the beam, andvarious magnetic lenses perform functions analagous to those of ordinarylenses in a light microscope.

The term “hydrogel” refers to the formation of a colloid in which thedisperse phase (colloid) has combined with the continuous phase (water)to produce a viscous jellylike product.

The term “hydrophilic” refers to having an affinity for, attracting,adsorbing, or absorbing water.

The term “hydrophobic” refers to lacking an affinity for, repelling, orfailing to adsorb or absorb water.

The term “lamellar phase” refers to one of the possible structuresformed by a surfactant depending on the surfactant and its concentrationcharacterized by a thin plate-like shape.

The term “lecithin” refers to any group of phospholipids having thegeneral composition CH₂OR₁CH₂OR₂CH₂OPO₂OHR₃, in which R₁ and R₂ arefatty acids and R₃ is choline, and emulsifying, wetting, and antioxidantproperties.

The term “lipophilic” refers to having a strong affinity for fats.

The term “liposome” refers to one of the fatty droplets occurring in thecytoplasm.

The term “micelle” refers to a colloidal aggregate of a unique number(between 50 and 100) of amphiphilic moledules.

The term “nanotube” refers to a hollowed out cylindrically shapedformation of atoms, molecules, or peptides of any length but with adiameter on the nanometer scale.

The term “neurite outgrowth” refers to the outgrouth of nerve fiber of aneuron that carries the unidirectional nerve impulse away from the cellbody.

The term “oligopeptide” refers to a peptide composed of no more than 10amino acids.

The term “physiological pH” refers to a pH of about 7.

The term “protecting group” as used herein means temporary substituentswhich protect a potentially reactive functional group from undesiredchemical transformations. Examples of such protecting groups includeesters of carboxylic acids, silyl ethers of alcohols, and acetals andketals of aldehydes and ketones, respectively. The field of protectinggroup chemistry has been reviewed (Greene, T. W.; Wuts, P.G.M.Protective Groups in Organic Synthesis, 2^(nd) ed.; Wiley: N.Y., 1991).

The term “pKa” refers to the negative logarithm of the acid equilibriumconstant. The lower the pKa the more acidic the acid is.

The term “self assembly” refers to the process of atoms, molecules, orpeptides to form regular shaped structures in response to the generalconditions of their environment.

Compounds of the Invention

In certain embodiments, the compounds of the present invention arerepresented by formulas 1-10: Sequence (N → C) Formula (φ)_(m)(+)_(n) 1(+)_(n)(φ)_(m) 2 (φ)_(m)(−)_(n) 3 (−)_(n)(φ)_(m) 4 (−)_(n)(φ)_(m)(−)_(n)5 (+)_(n)(φ)_(m)(+)_(n) 6 (φ)_(m)(−)_(n)(φ)_(m) 7 (φ)_(m)(+)_(n)(φ)_(m)8 (+)_(n)(φ)_(m)(−)_(n) 9 (−)_(n)(φ)_(m)(+)_(n) 10wherein

(φ) represents independently for each occurrence a natural ornon-natural amino acid comprising a nonpolar, noncharged sidechain;

(+) represents independently for each occurrence a natural ornon-natural amino acid comprising a sidechain that is cationic atphysiological pH;

(−) represents independently for each occurrence a natural ornon-natural amino acid comprising a sidechain that is anionic atphysiological pH;

m represents an integer greater than or equal to 5; and n represents aninteger greater than or equal to 1.

In certain embodiments, the compounds of formulas 5-10 are tri-blockpeptide co-polymers.

In certain embodiments, the present invention provides self assembledstructures from compounds of formulas 1-10.

In certain embodiments, the present invention provides goldnanostructures formed by localizing gold upon the self assembledstructures of the present invention.

In certain embodiments, the present invention provides a method ofdelivering guest compounds across a host membrane comprising the step ofadministering the guest compound within the self assembled structures ofthe present invention.

In certain embodiments, the present invention provides a method ofdelivering a drug across a host membrane comprising the step ofadministering the drug within the self assembled structures of thepresent invention.

In certain embodiments, the present invention provides a filter based onthe nanostructures of the present invention.

Nanotube Forming Peptides

Table 2 shows the different oligopeptides synthesized and investigatedso far. The hydrophilic moiety of the molecule is given by one or twoaspartic acids. Due to the method of synthesis, an additional carboxylicgroup is linked to the last aspartic acid. Consequently, the head grouphas potentially three negative charges. The lipophilic tail of thepeptides is constituted of six consecutive hydrophobic amino acids. Theshape and the global hydrophobicity of the peptide can thus beconveniently fine-tuned by increasing the aliphatic side group of theamino acid. The calculated pI for the investigated peptides gives valuefrom 3.56 to 3.8 depending on the number of aspartic acids constitutingthe hydrophilic head group. At pH under these values, the peptides aremainly protonated and, thus uncharged. Consequently, their solubilitiesin water are compromised. TABLE 2 Synthesized surfactant peptides of thecurrent invention Molecular Calcu- Sequence Weight lated Name N-terminus→ C-terminus [g/mol] pI A₆D [Acetyl]-AAAAAAD-CO₂ 557.6 3.80 V₆D[Acetyl]-VVVVVVD-CO₂ 725.9 3.80 A₆D₂ [Acetyl]-AAAAAADD-CO₂ 671.7 3.56V₆D₂ [Acetyl]-VVVVVVDD-CO₂ 840.0 3.56 L₆D₂ [Acetyl]-LLLLLLDD-CO₂ 924.13.56 K₂I₆ KKIIIIII-C(O)NH₂ K₂L₆ KKLLLLLL-C(O)NH₂ K₂A₆ KKAAAAAA-C(O)NH₂K₂V₆ KKVVVVVV-C(O)NH₂

Molecular models of the peptides synthetized are shown in the FIG. 1,where the hydrophobic part of the molecule is composed of alanine,valine, or leucine respectively. By changing the character of thehydrophobic side chains, we can induce a change in the intermolecularforces with which the tails can interact. In the first groupsurfactant-like polypeptides, the hydrophilic head group is keptunchanged and we only varied the hydrophobicity of side chain whilemaintaining the same number of amino acids (see FIG. 1). The alanine (A)side chain consists of one carbon whereas the valine (V) side chain hasthree carbon groups. The leucine (L) side chain has four carbons. V₆Dand A₆D were also synthesized in order to investigate the influence ofthe hydrophilic head group on the self-assembly behavior of this newclass of peptides. These two peptides are made of only one aspartic acidas hydrophilic head group and, consequently, carry two negative charges(C-terminal) instead of three for its analogs V₆D₂ or A6D₂. Besides thevariation in electrostatic interactions expected for such a modificationof the peptide sequence, the cross-sectional area (a) of the polar headgroup will be smaller, leading to a decrease in the packing parameter Pas describe by Israelachvili²¹ (P=v[al]¹, where v is the molecularvolume, l the molecular length and a is the cross-sectional area of thepolar head group).

Cryo-transmission electron microscopy experiments were performed onaqueous solution of the different peptides at a concentration of 5mg/mi. In order to solubilize these peptides in water, it was necessaryto deprotonate the carboxylic groups by adjusting the pH with a solutionof sodium hydroxide 0.1N. The oligopeptides investigated start to besoluble in water at pH 5 to 6, depending on the amino acid sequence. Allthe experiments presented in this work were carried out using peptidesolutions at pH 7. Cryo-TEM experiments for these systems indicated thatthe charged oligopeptides exist as a dense network of entanglednanotubes of diameter ranging from 25 nm to 50 nm (FIG. 2). Thecylindrical assemblers present a three-dimensional transient networksomehow similar-to flexible polymers in their semidilute or concentratedsolutions²². It should be pointed out that, in the electron micrographs,only a two-dimensional projection of the peptides nanotubes could beimaged. The network below and above a defined point in the space couldbe relatively distant in three dimensions, while appearing superimposedin the two-dimensional projection. This result in a denser appearance ofthe two-dimensional network. Cryo-TEM micrographs of V₆D, V₆D₂ and A₆Dexhibit very similar cylindrical morphologies. These self-assemblieshave high axial ratios and extend in length to several tens ofmicrometers. Additionally, one can easily identify many three-foldjunctions or branchings connecting the nanotubes and thus forming thefinal network. It seems that the branches connecting two nanotubes havecylindrical morphologies of smaller diameter (about 25 nm).Alternatively, two nanotubes could fuse together to form a tentative4-arm branch. It has been shown that this kind of branching isenergetically unstable and, thus, those observed in FIG. 3 are mostlikely due to the 2-D representation of a spatial network.

The possibility that branched supramolecular organizations exist hasattracted considerable interest²²⁻²⁴. Evidence of branching has mainlybeen reported for aqueous surfactant solutions but reversed structuresuch as lecithin organogels can also form three-fold junctions²³. Branchpoints produce patches having mean curvature opposite to that of theportion far from the junction²⁵. Many reports claimed the importance ofbranching points to visco-elastic properties of polymer-like systems²².Cates et al.²⁶⁻²⁷ have provided a statistical description of branchesvs. entanglements whereas Lequeux²⁸ has modeled the expected effects onthe Theological properties.

Cryo-TEM micrograph of A₆D₂ shows a slightly different pattern with adenser network. In fact, one can easily recognize nanotubes of about 50run diameter linked by an increased numbers of three-fold junction. As aresult, the branches are more abundant than those observed in thesamples V₆D, V₆D₂ and A₆D. They have also a smaller axial ratio and amuch smaller average diameter of about 10 to 15 nm. L₆D₂ is the mosthydrophobic compound with the tail constituted of six leucines. Aqueoussolution of L₆D₂ does not exhibit any nanotubular structures but rathera network of entangled rodlike micelles. These molecular assemblies arevery similar to threadlike micellar systems made from traditionalamphiphilic molecules such as cetyltrimethylammonium bromide(CTAB)29-30. It should be noted that a large number of vesicle-likespherical assemblies also appear in the TEM micrograph.

Cryo-TEM micrograph at high resolution provides a detailed structure ofthe peptide nanotubes formed by AAAAAAD (see FIG. 4). The presence ofhollow tubular structures is clearly visible under these conditions,giving rise to two spatially separated hydrophilic surfaces.Additionally, helical pitches between 150 and 200 nm, depending on thenanotubes diameter, were also observed. Similar results have beendocumented with hollow cylinders formed of bilayer membrane ofdiacetylenic lipids³¹. Theories based on molecular chirality have beendeveloped to explain the presence of helical markings that wind aroundthe cylinders³².

A possible structural organization is suggested by molecular modeling ofthe peptide nanotubes (FIG. 5). It is proposed that subunits rings arefirst formed through self-assembly of peptides monomers in bilayertopology, where hydrophilic head groups remain exposed to the continuousmedia. The cylindrical arrays can subsequently be stacked vianon-covalent interactions to form continuous tubes.

Tubular nanostructure made from self-assembly of this new class ofpolypeptide is only the first system discovered so far. It isanticipated that, very much like surfactant self-assemblies, fine-tuningof the monomer properties will give rise to a wide range ofnanostructures, thus opening new innovative avenues for the developmentof biomaterials. It is envisioned that a number of variables can beexamined. For example, increasing the length of the hydrophobic chainmay introduce more rigidity in the membranes and perhaps lead to tubesof greater diameter with smaller curvature. In the same way changing thecharacter of the hydrophobic side chains would be important. Usingphenol alanine, for example, will certainly change the fluidity of thehydrophobic phase and is likely to change the morphology and thedimensions of the network.

Experiments can also be carried out in which variations in the chargedresidue can be explored. We have already shown in a preliminary fashionthat putting two charged residues into the aqueous phase results inbuilding a similar structure. However, addition of a third chargedresidue de-stabilizes it, probably by making the individual moleculesoluble in water, thereby preventing the self-association intomembranes. Thus, one of the elements to be explored systematically isthe relative balance of the hydrophobic chain, versus the hydrophilicends. It is possible that the use of longer hydrophobic segments couldstabilize the membrane so that we could introduce many more variationsin the hydrophilic end. The kind of experiments that could be carriedout might involve the use of a mixture of positively charged andnegatively charged residues in the hydrophilic end with the samehydrophobic tail. This might lead to development of a differentorganization of the tubes. By changing the ratio of positive tonegative, it is likely that we will be able to control some elements ofthe self-assembly and therefore control the morphology of the nanotubes.

Work on this novel assembly mode is just underway, and one of our firstgoals is to obtain more physical evidence about the nature of theaggregation. In this regard, solution X-ray diffraction photographs willbe useful in understanding elements of the packing. By substitutingbromine or iodine atoms in the hydrophilic end, we could then determinethe distance between these heavy atoms in the X-ray scattering diagramand in this way draw inferences about the nature of the assembly. Asystematic series of studies of this type in which the hydrophobic tailis elongated would provide the necessary information about theorganization of these nanotubes.

Through the use of longer and possibly less flexible hydrophobic chains,it may be possible to begin to build structures on the hydrophilicsurface of the nanotube by extending the peptide chain, for example, tomake small α-helical segments. Research of this type could lead to thedevelopment of nanotubes with textured surfaces, that is, surfaces inwhich a series of different structural motifs could be investigated. Forexample, helices or even β-sheet structures could be assembled on theoutside of the membrane. The driving force in forming the membrane isthe hydrophobicity of the hydrophobic peptide. One of the elements thatwould be of interest to explore is the use of block co-polymers in thehydrophobic phase. For example, imagine a system made with the generalformula f_(n)a_(m) that has a hydrophobic tail in which n-phenolalanines are linked to m-alanines. This hydrophobic tail would have arather large anchor of phenol alanine rings at one end. The use of astructured hydrophobic anchor of this type would make it possible toexplore the effects of having these residues assembled in oppositeorientation with the hydrophobic residues at either end. In this way onemight in effect “lock” the hydrophobic domains together by having bulkyphenol alanine residues at one end and less bulky or slimmer alanineresidues at the other end. This should have a significant effect inproducing a membrane that is more rigid and perhaps capable of formingvery large tubes with a considerably greater radius of curvature.

At this stage the inventors realize that a variety of differentnanosheets and nanotubes can be engineered through the use of the greatdeal of chemical variation found in the 20 different amino acids.

Peptide Di- and Tri-Block Co-Polymers

Block co-polymers using organic compounds have emerged as a very welldeveloped system to construct new materials that have a broad range ofapplications. This system can be readily extended to biological buildingmaterials. There are 20 natural L-amino acids, their mirror image ofD-amino acids and a variety of non-natural amino acids, all of which canbe readily used as the building blocks to construct the bio-based blockco-polymers.

There are a number of advantages to build these biological blockco-polymers using the well-developed synthetic chemistry: 1) these blockco-polymers are amenable for molecular systematic design, modification,and synthesis; 2) these designed block co-polymers can be subjected toextensive molecular modeling and simulations before synthesis; 3) theseblock co-polymers can be highly purified to be mono-dispersed materials;4) a combinatorial approach can be employed to systematicallycharacterize these co-polymers at various ratios; 5) instrumentationthat has been used for polymer research can be readily used tocharacterize the biological block co-polymer; 6) these nanobuildingblocks can be used to construct a number of unexpected and interestingmaterials; and 7) the peptides can also be synthesized in vitro or invivo.

Many block copolymer-like motifs have been found in proteins. Some ofwhich are important for the protein biological function and others havebeen used as a tool for discovery of new proteins in cells. Research inthis under-explored area will likely produce some unexpected findingsthat can not only provide us with new knowledge of complexity in polymerscience but may also provide insight into protein-protein interactionsand protein folding. These bio-based block co-polymers may be developedfor a variety of applications. Since the combinations are extremelylarge, formulas 1-10 describe the generic block copolymer sequences andtwo tables listing the peptide block copolymers are presented in Tables3 and 4. Sequence (N → C) Formula (φ)_(m)(+)_(n) 1 (+)_(n)(φ)_(m) 2(φ)_(m)(−)_(n) 3 (−)_(n)(φ)_(m) 4 (−)_(n)(φ)_(m)(−)_(n) 5(+)_(n)(φ)_(m)(+)_(n) 6 (φ)_(m)(−)_(n)(φ)_(m) 7 (φ)_(m)(+)_(n)(φ)_(m) 8(+)_(n)(φ)_(m)(−)_(n) 9 (−)_(n)(φ)_(m)(+)_(n) 10

Where (+), (−), (φ), m, and n are defined as before. TABLE 3 SynthesizedDi-Block Co-Polymers. No. of Name residues Sequence (N → C) DA20 20−−−−−−−−− DDDDDDDDDDAAAAAAAAAA AD20 20           −−−−−−−−−AAAAAAAAAADDDDDDDDDD AE20 20 −−−−−−−−− EEEEEEEEEEAAAAAAAAAA EA20 20          −−−−−−−− AAAAAAAAAAEEEEEEEEEE DV20 20 −−−−−−−−−−DDDDDDDDDDVVVVVVVVVV VD20 20           −−−−−−−−− VVVVVVVVVVDDDDDDDDDDDP20 20 −−−−−−−−−− DDDDDDDDDDPPPPPPPPPP PD20 20           −−−−−−−−−PPPPPPPPPPDDDDDDDDDD HA20 20           +++++++++ AAAAAAAAAHHHHHHHHHHHAH20 20 +++++++++ HHHHHHHHHHAAAAAAAAAA KA20 20 +++++++++KKKKKKKKKKAAAAAAAAAA AK20 20           +++++++++ AAAAAAAAAAKKKKKKKKKKRA20 20 ++++++++ RRRRRRRRRRAAAAAAAAAA AR20 20           +++++++++AAAAAAAAAARRRRRRRRRRD is aspartic acid; A is alanine; E is glutamic acid; V is valine; P isproline; H is histidine; K is lysine; and R is arginine.

TABLE 4 Synthesized Tri-Block Co-Polymers. No. of Name residues Sequence(N → C) DAD30 30 −−−−−−−−−−          −−−−−−−−−−DDDDDDDDDDAAAAAAAAAADDDDDDDDDD ADA30 30           −−−−−−−−−−AAAAAAAAAADDDDDDDDDDAAAAAAAAAA AEA30 30 −−−−−−−−−−          −−−−−−−−−−EEEEEEEEEEAAAAAAAAAAEEEEEEEEEE EAE30 30           −−−−−−−−−−AAAAAAAAAAEEEEEEEEEEAAAAAAAAAA DVD30 30 −−−−−−−−−−          −−−−−−−−−−DDDDDDDDDDVVVVVVVVVVDDDDDDDDDD VDV30 30           −−−−−−−−−−VVVVVVVVVVDDDDDDDDDDVVVVVVVVVV DP30 30 −−−−−−−−−−          −−−−−−−−−−DDDDDDDDDDPPPPPPPPPPDDDDDDDDDD PDP30 30           −−−−−−−−−−PPPPPPPPPPDDDDDDDDDDPPPPPPPPPP HAH30 30           ++++++++++AAAAAAAAAAHHHHHHHHHHAAAAAAAAAA AHA30 30 ++++++++++          ++++++++++HHHHHHHHHHAAAAAAAAAAHHHHHHHHHH KAK30 30 ++++++++++          ++++++++++KKKKKKKKKKAAAAAAAAAAKKKKKKKKKK AKA30 30           ++++++++++AAAAAAAAAAKKKKKKKKKKAAAAAAAAAA RAR30 30 ++++++++++          ++++++++++RRRRRRRRRRAAAAAAAAAARRRRRRRRRR ARA30 30           ++++++++++AAAAAAAAAARRRRRRRRRRAAAAAAAAAA KAD30 30 ++++++++++          −−−−−−−−−−KKKKKKKKKKAAAAAAAAAADDDDDDDDDD KAE30 30 ++++++++++          −−−−−−−−−−KKKKKKKKKKAAAAAAAAAAEEEEEEEEEE RVD30 30 ++++++++++          −−−−−−−−−−RRRRRRRRRRVVVVVVVVVVDDDDDDDDDD KPD30 30 ++++++++++          −−−−−−−−−−KKKKKKKKKKPPPPPPPPPPDDDDDDDDDD HAE30 30 ++++++++++          −−−−−−−−−−HHHHHHHHHHAAAAAAAAAAEEEEEEEEEED is aspartic acid; A is alanine; E is glutamic acid; V is valine; P isproline; H is histidine; K is lysine; and R is arginine.Forming Gold Nanostructures

The ability of sulfur to form covalent bonds with gold surfaces is welldocumented in the art¹. The interaction between gold and suchsulfur-containing functional groups is a well-studied science, and anonlimiting representative exemplary list of such sulfur-containingfunctionalities may be found in an article entitled “Wet ChemicalApproaches to the Characterization of Organic Surfaces: Self-AssembledMonolayers, Wetting and the Physical-Organic Chemistry of theSolid-Liquid Interface” by G. W. Whitesides and Paul E. Laibinis,Langmuir, 6, 87 (1990), incorporated herein by reference. Some generalconcepts can be garnered from the literature and include the following.Any functional group terminated with a sulfur (R-S) can be assembled ongold; sulfur coordinates strongly to gold which allows monolayerformation in the presence of many other functional groups; gold isresistant to oxidation, which often inhibits monolayer assembly on othermaterials; and monolayers pack densely on gold.

The current invention is particularly well suited to exploit thischemistry. Particularly preferred in the present invention is a goldsurface, and a thiol. Modification of the nanotube walls can be carriedout by selectively choosing amino acids of different properties.Substitution of one of the amino acids listed in any of the previouscompounds with the amino acid cysteine with its thiol -SH functionalitygives the potential of both anchoring the nanotubes upon a gold surfaceand incorporating a gold coating upon the nanotubes. The gold coatingcan be applied via electroplating gold in the presence of cysteineincluding nanotubes. Importantly, the gold-bearing peptides mayconstitute only a portion of the peptides making up a given nanotube.

One novel application of this technology would be to use radio frequencyenergy to open a gold-bearing nanotube, thereby releasing its contents.For example, this approach may be utilized on gold-bearing nanotubesthat contain a drug, thereby releasing the drug within an organism thathas ingested or been injected with the aforementioned gold-bearingnanotube.

Another novel application would be in the field of molecular wires,where gold particles can be organized by the peptide nanotubes into awire, and the wires can be fabricated into a circuit.

Filtration Systems Based on Nanotubes

Filtration systems based on both size and charge lend themselves verywell to the current invention. The oligopeptide nanotubes of the currentinvention form with regular diameters on the order of 50 nm. However, aswith surfactants, increasing the length of the hydrophobic tail may leadto a more rigid nanotube and larger tubular diameter. Separation ofmacromolecules from small molecules is the basis of dialysis and it isenvisioned by the inventors that the current invention will lead totailor made filtration systems for separating molecules based on size.Additionally, the charge of the internal core is adjustable byselectively choosing the amino acids that make up the head portion ofthe oligopeptide. This would allow filtration based not on size but oncharge. For instance, a nanotube with a predominantly anionic head wouldallow cations to pass but repel anions. Likewise, a nanotube with apredominantly cationic head would allow anions to pass but not cations.

Delivery of Guest/Drug Compounds

The nanotubes of the present invention can be carriers for bilogicallyactive materials. Temporary preservation of functional properties of acarried species, as well as controlled release of the species into localtissues or systemic circulation, are possible. Proper choice of aminoacids can produce nanotubes with a range of permeability and diametersizes suitable for a variety of applications in medical treatments. Inan analogous manner to cationic liposomes, positively charged compoundof the present invention can be used to deliver genes via plasmids.Conversely, negatively charged compounds of the invention can be used todeliver positively charged guests. The current invention is superior toliposome delivery systems in that the nanotubes fuse with the lipidbilayers and do not deform the cell as do liposomes.

Pharmaceutical Compositions

In another aspect, the present invention provides pharmaceuticallyacceptable compositions which comprise a therapeutically-effectiveamount of one or more of the compounds described above, formulatedtogether with one or more pharmaceutically acceptable carriers(additives) and/or diluents. As described in detail below, thepharmaceutical compositions of the present invention may be speciallyformulated for administration in solid or liquid form, including thoseadapted for the following: (1) oral administration, for example,drenches (aqueous or non-aqueous solutions or suspensions), tablets,boluses, powders, granules, pastes for application to the tongue; (2)parenteral administration, for example, by subcutaneous, intrarnuscularor intravenous injection as, for example, a sterile solution orsuspension; (3) topical application, for example, as a cream, ointmentor spray applied to the skin; or (4) intravaginally or intrarectally,for example, as a pessary, cream or foam.

The phrase “therapeutically-effective amount” as used herein means thatamount of a compound, material, or composition comprising a compound ofthe present invention which is effective for producing some desiredtherapeutic effect in at least a sub-population of cells in an animal ata reasonable benefit/risk ratio applicable to any medical treatment.

The phrase “pharmaceutically acceptable” is employed herein to refer tothose compounds, materials, compositions, and/or dosage formns whichare, within the scope of sound medical judgment, suitable for use incontact with the tissues of human beings and animals without excessivetoxicity, irritation, allergic response, or other problem orcomplication, commensurate with a reasonable benefit/risk ratio.

The phrase “pharmaceutically-acceptable carrer” as used herein means apharmnaceutically-acceptable material, composition or vehicle, such as aliquid or solid filler, diluent, excipient, solvent or encapsulatingmaterial, involved in carrying or transporting the subject compound fromone organ, or portion of the body, to another organ, or portion of thebody. Each carrier must be “acceptable” in the sense of being compatiblewith the other ingredients of the formulation and not injurious to thepatient. Some examples of materials which can serve aspharmaceutically-acceptable carriers include: (1) sugars, such aslactose, glucose and sucrose; (2) starches, such as corn starch andpotato starch; (3) cellulose, and its derivatives, such as sodiumcarboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4)powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients,such as cocoa butter and suppository waxes; (9) oils, such as peanutoil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil andsoybean oil; (10) glycols, such as propylene glycol; (11) polyols, suchas glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters,such as ethyl oleate and ethyl laurate; (13) agar; (14) bufferingagents, such as magnesium hydroxide and aluminum hydroxide; (15) alginicacid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer'ssolution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21)other non-toxic compatible substances employed in pharmaceuticalformulations.

As set out above, certain embodiments of the present compounds maycontain a basic functional group, such as amino or alkylamino, and are,thus, capable of forming pharnaceutically-acceptable salts withpharmaceutically-acceptable acids. The term “pharmaceutically-acceptablesalts” in this respect, refers to the relatively non-toxic, inorganicand organic acid addition salts of compounds of the present invention.These salts can be prepared in situ during the final isolation andpurification of the compounds of the invention, or by separatelyreacting a purified compound of the invention in its free base form witha suitable organic or inorganic acid, and isolating the salt thusformed. Representative salts include the hydrobromide, hydrochloride,sulfate, bisulfate, phosphate, nitrate, acetate, valerate, oleate,palmitate, stearate, laurate, benzoate, lactate, phosphate, tosylate,citrate, maleate, fumarate, succinate, tartrate, napthylate, mesylate,glucoheptonate, lactobionate, and laurylsulphonate salts and the like.(See, for example, Berge et al. (1977) “Pharmaceutical Salts”, J. Pharm.Sci. 66:1-19)

The pharmaceutically acceptable salts of the subject compounds includethe conventional nontoxic salts or quaternary ammonium salts of thecompounds, e.g., from non-toxic organic or inorganic acids. For example,such conventional nontoxic salts include those derived from inorganicacids such as hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric,nitric, and the like; and the salts prepared from organic acids such asacetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric,citric, ascorbic, pahmitic, maleic, hydroxymaleic, phenylacetic,glutamic, benzoic, salicyclic, sulfanilic, 2-acetoxybenzoic, fumaric,toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isothionic,and the like.

In other cases, the compounds of the present invention may contain oneor more acidic functional groups and, thus, are capable of formingpharmaceutically-acceptable salts with pharmaceutically-acceptablebases. The term “pharmaceutically-acceptable salts” in these instancesrefers to the relatively non-toxic, inorganic and organic base additionsalts of compounds of the present invention. These salts can likewise beprepared in situ during the final isolation and purification of thecompounds, or by separately reacting the purified compound in its freeacid form with a suitable base, such as the hydroxide, carbonate orbicarbonate of a phannaceutically-acceptable metal cation, withamrnonia, or with a pharmaceutically-acceptable organic primary,secondary or tertiary amine. Representative alkali or alkaline earthsalts include the lithium, sodium, potassium, calcium, magnesium, andaluminum salts and the like. Representative organic amines useful forthe formation of base addition salts include ethylamine, diethylamine,ethylenediamine, ethanolamine, diethanolamine, piperazine and the like.(See, for example, Berge et al., supra)

Wetting agents, emulsifiers and-lubricants, such as sodium laurylsulfate and magnesium stearate, as well as coloring agents, releaseagents, coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the compositions.

Examples of pha.naceutically-acceptable antioxidants include: (1) watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2)oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and (3) metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Formulations of the present invention include those suitable for oral,nasal, topical (including buccal and sublingual), rectal, vaginal and/orparenteral administration. The formulations may conveniently bepresented in unit dosage form and may be prepared by any methods wellknown in the art of pharmacy. The amount of active ingredient which canbe combined with a carrier material to produce a single dosage form willvary depending upon the host being treated, the particular mode ofadministration. The amount of active ingredient which can be combinedwith a carrier material to produce a single dosage form will generallybe that amount of the compound which produces a therapeutic effect.Generally, out of one hundred per cent, this amount will range fromabout 1 per cent to about ninety-nine percent of active ingredient,preferably from about 5 per cent to about 70 per cent, most preferablyfrom about 10 per cent to about 30 per cent.

Methods of preparing these formulations or compositions include the stepof bringing into association a compound of the present invention withthe carrier and, optionally, one or more accessory ingredients. Ingeneral, the formulations are prepared by uniformly and intimatelybringing into association a compound of the present invention withliquid carriers, or finely divided solid carriers, or both, and then, ifnecessary, shaping the product.

Formulations of the invention suitable for oral administration may be inthe form of capsules, cachets, pills, tablets, lozenges (using aflavored basis, usually sucrose and acacia or tragacanth), powders,granules, or as a solution or a suspension in an aqueous or non-aqueousliquid, or as an oil-in-water or water-in-oil liquid emulsion, or as anelixir or syrup, or as pastilles (using an inert base, such as gelatinand glycerin, or sucrose and acacia) and/or as mouth washes and thelike, each containing a predetermined amount of a compound of thepresent invention as an active ingredient. A compound of the presentinvention may also be administered as a bolus, electuary or paste.

In solid dosagc forms of the invention for oral administration(capsules, tablets, pills, dragees, powders, granules and the like), theactive ingredient is mixed with one or more pharmaceutically-acceptablecarriers, such as sodium citrate or dicalcium phosphate, and/or any ofthe following: (1) fillers or extenders, such as starches, lactose,sucrose, glucose, mannitol, and/or silicic acid; (2) binders, such as,for example, carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone, sucrose and/or acacia; (3) humectants, such as glycerol;(4) disintegrating agents, such as agar-agar, calcium carbonate, potatoor tapioca starch, alginic acid, certain silicates, and sodiumcarbonate; (5) solution retarding agents, such as paraffin; (6)absorption accelerators, such as quatemary. ammonium compounds; (7)wetting agents, such as, for example, cetyl alcohol and glycerolmonostearate; (8) absorbents, such as kaolin and bentonite clay; (9)lubricants, such a talc, calcium stearate, magnesium stearate, solidpolyethylene glycols, sodium lauryl sulfate, and mixtures thereof; and(10) coloring agents. In the case of capsules, tablets and pills, thepharmaceutical compositions may also comprise buffering agents. Solidcompositions of a similar type may also be employed as fillers in softand hard-filled gelatin capsules using such excipients as lactose ormilk sugars, as well as high molecular weight polyethylene glycols andthe like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared usingbinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-active or dispersing agent. Molded tablets may be made bymolding in a suitable machine a mixture of the powdered compoundmoistened with an inert liquid diluent.

The tablets, and other solid dosage forms of the pharmaceuticalcompositions of the present invention, such as dragees, capsules, pillsand granules, may optionally be scored or prepared with coatings andshells, such as enteric coatings and other coatings well known in thepharmaceutical-formulating art. They may also be formulated so as toprovide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile, other polymer matrices,liposomes and/or microspheres. They may be sterilized by, for example,filtration through a bacteria-retaining filter, or by incorporatingsterilizing agents in the form of sterile solid compositions which canbe dissolved in sterile water, or some other sterile injectable mediumimmediately before use. These compositions may also optionally containopacifying agents and may be of a composition that they release theactive ingredient(s) only, or preferentially, in a certain portion ofthe gastrointestinal tract, optionally, in a delayed manner. Examples ofembedding compositions which can be used include polymeric substancesand waxes. The active ingredient can also be in micro-encapsulated form,if appropriate, with one or more of the above-described excipients.

Liquid dosage forms for oral administration of the compounds of theinvention include pharmaceutically acceptable emulsions, microemulsions,solutions, suspensions, syrups and elixirs. In addition to the activeingredient, the liquid dosage forms may contain inert diluents commonlyused in the art, such as, for example, water or other solvents,solubilizing agents and emulsifiers, such as ethyl alcohol, isopropylalcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzylbenzoate, propylene glycol, 1,3-butylene glycol, oils (in particular,cottonseed, groundnut, corn, germ, olive, castor and sesame oils),glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acidesters of sorbitan, and mixtures thereof.

Besides inert diluents, the oral compositions can also include adjuvantssuch as wetting agents, emulsifying and suspending agents, sweetening,flavoring, coloring, perfuming and preservative agents.

Suspensions, in addition to the active compounds, may contain suspendingagents as, for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminummetahydroxide, bentonite, agar-agar and tragacanth, and mixturesthereof.

Formulations of the pharmaceutical compositions of the invention forrectal or vaginal administration may be presented as a suppository,which may be prepared by mixing one or more compounds of the inventionwith one or more suitable nonirritating excipients or carrierscomprising, for example, cocoa butter, polyethylene glycol, asuppository wax or a salicylate, and which is solid at room temperature,but liquid at body temperature and, therefore, will melt in the rectumor vaginal cavity and release the active compound.

Formulations of the present invention which are suitable for vaginaladministration also include pessaries, tampons, creams, gels, pastes,foams or spray formulations containing such carriers as are known in theart to be appropriate.

Dosage forms for the topical or transdermnal administration of acompound of this invention include powders, sprays, ointments, pastes,creams, lotions, gels, solutions, patches and inhalants. The activecompound may be mixed under sterile conditions with apharmaceutically-acceptable carrier, and with any preservatives,buffers, or propellants which may be required.

The ointments, pastes, creams and gels may contain, in addition to anactive compound of this invention, excipients, such as animal andvegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulosederivatives, polyethylene glycols, silicones, bentonites, silicic acid,talc and zinc oxide, or mixtures thereof.

Powders and sprays can contain, in addition to a compound of thisinvention, excipients such as lactose, talc, silicic acid, aluminumhydroxide, calcium silicates and polyamide powder, or mixtures of thesesubstances. Sprays can additionally contain customary propellants, suchas chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons,such as butane and propane.

Transdermal patches have the added advantage of providing controlleddelivery of a compound of the present invention to the body. Such dosageforms can be made by dissolving or dispersing the compound in the propermedium. Absorption enhancers can also be used to increase the flux ofthe compound across the skin. The rate of such flux can be controlled byeither providing a rate controlling membrane or dispersing the compoundin a polymer matrix or gel.

Ophthalmic formulations, eye ointments, powders, solutions and the like,are also contemplated as being within the scope of this invention.

Pharmaceutical compositions of this invention suitable for parenteraladministration comprise one or more compounds of the invention incombination with one or more pharmaceutically-acceptable sterileisotonic aqueous or nonaqueous solutions, dispersions, suspensions oremulsions, or sterile powders which may be reconstituted into sterileinjectable solutions or dispersions just prior to use, which may containantioxidants, buffers, bacteriostats, solutes which render theformulation isotonic with the blood of the intended recipient orsuspending or thickening agents.

Examples of suitable aqueous and nonaqueous carriers which may beemployed in the pharmaceutical compositions of the invention includewater, ethanol, polyols (such as glycerol, propylene glycol,polyethylene glycol, and the like), and suitable mixtures thereof,vegetable oils, such as olive oil, and injectable organic esters, suchas ethyl oleate. Proper fluidity can be maintained, for example, by theuse of coating materials, such as lecithin, by the maintenance of therequired particle size in the case of dispersions, and by the use ofsurfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms upon the subject compounds may be ensuredby the inclusion of various antibacterial and antifungal agents, forexample, paraben, chlorobutanol, phenol sorbic acid, and the like. Itmay also be desirable to include isotonic agents, such as sugars, sodiumchloride, and the like into the compositions. In addition, prolongedabsorption of the injectable pharmaceutical form may be brought about bythe inclusion of agents which delay absorption such as aluminummonostearate and gelatin.

In some cases, in order to prolong the effect of a drug, it is desirableto slow the absorption of the drug from subcutaneous or intramuscularinjection. This may be accomplished by the use of a liquid suspension ofcrystalline or amorphous material having poor water solubility. The rateof absorption of the drug then depends upon its rate of dissolutionwhich, in turn, may depend upon crystal size and crystalline form.Alternatively, delayed absorption of a parenterally-administered drugform is accomplished by dissolving or suspending the drug in an oilvehicle.

Injectable depot forms are made by forming microencapsule matrices ofthe subject compounds in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug in liposomes ormicroemulsions which are compatible with body tissue.

When the compounds of the present invention are administered aspharmaceuticals, to humans and animals, they can be given per se or as apharmaceutical composition containing, for example, 0.1 to 99.5% (morepreferably, 0.5 to 90%) of active ingredient in combination with apharmaceutically acceptable carrier.

The preparations of the present invention may be given orally,parenterallv, topically, or rectally. They are of course given in formssuitable for each administration route. For example, they areadministered in tablets or capsule form, by injection, inhalation, eyelotion, ointment, suppository, etc. administration by injection,infusion or inhalation; topical by lotion or ointment; and rectal bysuppositories. Oral administrations are preferred.

The phrases “parenteral administration” and “administered parenterally”as used herein means modes of administration other than enteral andtopical administration, usually by injection, and includes, withoutlimitation, intravenous, intramuscular, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intraarticulare, subcapsular,subarachnoid, intraspinal and intrastemal injection and infusion.

The phrases “systemic administration,” “administered systemically,”“peripheral administration” and “administered peripherally” as usedherein mean the administration of a compound, drug or other materialother than directly into the central nervous system, such that it entersthe patient's system and, thus, is subject to metabolism and other likeprocesses, for example, subcutaneous administration.

These compounds may be administered to humans and other animals fortherapy by any suitable route of administration, including orally,nasally, as by, for example, a spray, rectally, intravaginally,parenterally, intracisternally and topically, as by powders, ointmentsor drops, including buccally and sublingually.

Regardless of the route of administration selected, the compounds of thepresent invention, which may be used in a suitable hydrated form, and/orthe pharmaceutical compositions of the present invention, are formulatedinto pharmaceutically-acceptable dosage forms by conventional methodsknown to those of skill in the art.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of this invention may be varied so as to obtain an amountof the active ingredient which is effective to achieve the desiredtherapeutic response for a particular patient, composition, and mode ofadministration, without being toxic to the patient.

The selected dosage level will depend upon a variety of factorsincluding the activity of the particular compound of the presentinvention employed, or the ester, salt or amide thereof, the route ofadministration, the time of administration, the rate of excretion of theparticular compound being employed, the duration of the treatment, otherdrugs, compounds and/or materials used in combination with theparticular compound employed, the, age, sex, weight, condition, generalhealth and prior medical history of the patient being treated, and likefactors well known in the medical arts.

A physician or veterinarian having ordinary skill in the art can readilydetermine and prescribe the effective amount of the pharmaceuticalcomposition required. For example, the physician or veterinarian couldstart doses of the compounds of the invention employed in thepharmaceutical composition at levels lower than that required in orderto achieve the desired therapeutic effect and gradually increase thedosage until the desired effect is achieved.

In general, a suitable daily dose of a compound of the invention will bethat amount of the compound which is the lowest dose effective toproduce a therapeutic effect. Such an effective dose will generallydepend upon the factors described above. Generally, intravenous,intracerebroventricular and subcutaneous doses of the compounds of thisinvention for a patient, when used for the indicated analgesic effects,will range from about 0.0001 to about 100 mg per kilogram of body weightper day.

If desired, the effective daily dose of the active compound may beadministered as two, three, four, five, six or more sub-dosesadministered separately at appropriate intervals throughout the day,optionally, in unit dosage forms.

While it is possible for a compound of the present invention to beadministered alone, it is preferable to administer the compound as apharmaceutical formulation (composition).

In another aspect, the present invention provides pharmaceuticallyacceptable compositions which comprise a therapeutically-effectiveamount of one or more of the subject co,pounds, as described above,formulated together with one or more pharmaceutically acceptablecarriers (additives) and/or diluents. As described in detail below, thepharmaceutical compositions of the present invention may be speciallyformulated for administration in solid or liquid form, including thoseadapted for the following: (1) oral administration, for example,drenches (aqueous or non-aqueous solutions or suspensions), tablets,boluses, powders, granules, pastes for application to the tongue; (2)parenteral administration, for example, by subcutaneous, intramuscularor intravenous injection as, for example, a sterile solution orsuspension; (3) topical application, for example, as a cream, ointmentor spray applied to the skin; or (4) intravaginally or intravectally,for example, as a pessary, cream or foam.

The compounds according to the invention may be formulated foradministration in any convenient way for use in human or veterinarymedicine, by analogy with other pharmaceuticals.

The term “treatment” is intended to encompass also prophylaxis, therapyand cure.

The patient receiving this treatment is any animal in need, includingprimates, in particular humans, and other mammals such as equines,cattle, swine and sheep; and poultry and pets in general.

The compound of the invention can be administered as such or inadmixtures with pharmaceutically acceptable carriers and can also beadministered in conjunction with antimicrobial agents such aspenicillins, cephalosporins, aminoglycosides and glycopeptides.Conjunctive therapy, thus includes sequential, simultaneous and separateadministration of the active compound in a way that the therapeuticaleffects of the first administered one is not entirely disappeared whenthe subsequent is administered.

The addition of the active compound of the invention to animal feed ispreferably accomplished by preparing an appropriate feed premixcontaining the active compound in an effective amount and incorporatingthe premix into the complete ration.

Alternatively, an intermediate concentrate or feed supplement containingthe active ingredient can be blended into the feed. The way in whichsuch feed premixes and complete rations can be prepared and administeredare described in reference books (such as “Applied Animal Nutrition”, W.H. Freedman and CO., San Francisco, U.S.A., 1969 or “Livestock Feeds andFeeding” O and B books, Corvallis, Oreg., U.S.A., 1977).

Incorporation By Reference

All of the patents and publications cited herein are hereby incorporatedby reference.

Equivalents

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

REFERENCES

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1. A compound of formula(Φ)_(m)(+)_(n)1(N→C) wherein: (Φ) represents independently for each occurrence anatural or non-natural amino acid comprising a nonpolar, nonchargedsidechain; (+) represents independently for each occurrence a natural ornon-natural amino acid comprising a sidechain that is cationic atphysiological pH; m represents an integer greater than or equal to 5;and n represents an integer greater than or equal to 1.